Reaction of β-amino-α,β-unsaturated esters and amides with aryl diazonium salts : Synthesis of cinnoline derivatives

Conjugated esters and amides react with aryldiazonium salts at room temperature (MeCN) to form the corresponding iminium hydrazone derivatives, which can be thermally cyclized to cinnoline-3-esters and cinnoline-3-amides. In general the intermediate iminium salts derived from the enamine amides cyclize faster than those from the enamine esters. Furthermore, the ease of cyclization depends upon the structure of the base-component of the enamine ester or the amide and the substituent in the aryl moiety of the diazonium salt. The configurational structure of the iminium hydrazones, studied by NMR spectroscopy, has been shown to involve H-bonding of the hydrazonyl N-H with the ester or the amide CO group.     

Elastic instabilities for strain-stiffening rubber-like spherical and cylindrical thin shells under inflation

This paper is concerned with investigation of the effects of strain-stiffening on the classical limit point instability that is well-known to occur in the inflation of internally pressurized rubber-like spherical thin shells (balloons) and circular cylindrical thin tubes composed of incompressible isotropic non-linearly elastic materials. For a variety of specific strain-energy densities that give rise to strain-stiffening in the stress-stretch response, the inflation pressure versus stretch relations are given explicitly and the non-monotonic character of the inflation curves is examined. While such results are known for constitutive models that exhibit a gradual stiffening (e.g. exponential and power-law models), our primary focus is on materials that undergo severe strain-stiffening in the stress-stretch response. In particular, we consider two phenomenological constitutive models that reflect limiting chain extensibility at the molecular level. It is shown that for materials with sufficiently low extensibility no limit point instability occurs and so stable inflation is then predicted for such materials. Potential applications of the results to the biomechanics of soft tissues are indicated.     

Precipitation of palladium dimethyl-glyoximate from homogeneous solution

Palladium can be quantitatively precipitated from homogeneous solution with dimethylglyoxime generated by the reaction between biacetyl and hydroxylamine. The chelate is precipitated as long yellow needles which are easy to filter and wash. The separation of palladium from platinum and nickel was investigated.     

A New Method for Measuring Displacements of Micro Devices by an Optical Encoding System

Micro electro mechanical systems (MEMS) frequently require displacement measurements with high accuracy, a high sampling rate, and a long sensing travel. However, the available methods for measuring displacements of micro devices are typically limited in terms of at least one of these figures of merit. In this paper, we present a novel implementation of an optical encoding method for measuring displacements of micro devices that provides good capabilities in all of these figures of merit. The optical encoding system combines a commercial reading apparatus with a custom-made metal grating that can be easily produced during MEMS fabrication. Experimental tests demonstrate the ability of the system to measure displacements with a resolution of 25 nm and sampling rate of 1 MHz, under a variety of displacement rate functions.     

Shape resonances in slow electron scattering by aromatic molecules. I. Anthraquinone derivatives

A series of anthraquinone (C(14)O(2)H(8)) derivatives has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), photoelectron spectroscopy (PES), and AM1 quantum chemical calculations. Mean lifetimes of molecular negative ions M(-.) (MNI) have been measured. The mechanism of long-lived MNI formation in the epithermal energy region of incident electrons has been investigated. A simple model of a molecule (a spherical potential well with the repulsive centrifugal term) has been applied for the analysis of the energy dependence of cross sections at the first stage of the electron capture process. It has been shown that a temporary resonance of MNI at the energy approximately 0.5 eV corresponds to a shape resonance with lifetime 1-2.10(-13) s in the f-partial wave (l = 3) of the incident electron. The next resonant state of MNI at the energy approximately 1.7 eV has been associated with the electron excited Feshbach resonance (whose parent state is a triplet npi* transition). In all cases the initial electron state of the MNI relaxes into the ground state by means of a radiationless transition, and the final state of the MNI is a nuclear excited resonance with a lifetime measurable on the mass spectrometry timescale. Copyright 1999 John Wiley & Sons, Ltd.     

Plane strain bending of strain-stiffening rubber-like rectangular beams

This paper is concerned with investigation of the effects of strain-stiffening for the classical problem of plane strain bending by an end moment of a rectangular beam composed of an incompressible isotropic nonlinearly elastic material. For a variety of specific strain-energy densities that give rise to strain-stiffening in the stress–stretch response, the stresses and resultant moments are obtained explicitly. While such results are well known for classical constitutive models such as the Mooney-Rivlin and neo-Hookean models, our primary focus is on materials that undergo severe strain-stiffening in the stress–stretch response. In particular, we consider in detail two phenomenological constitutive models that reflect limiting chain extensibility at the molecular level and involve constraints on the deformation. The amount of bending that beams composed of such materials can sustain is limited by the constraint. Potential applications of the results to the biomechanics of soft tissues are indicated.     

A finite element formulation for global linear stability analysis of a nominally two‐dimensional base flow

A stabilized finite element method, to carry out the linear stability analysis of a two‐dimensional base flow to three‐dimensional perturbations that are periodic along span, is presented. The resulting equations for the time evolution of the disturbance requires a solution to the generalized eigenvalue problem. The analysis is global in nature and is also applicable to non‐parallel flows. Equal‐order‐interpolation functions for velocity and pressure are utilized. Stabilization terms are added to the Galerkin formulation to admit the use of equal‐order‐interpolation functions and to eliminate node‐to‐node oscillations that might arise in advection‐dominated flows. The proposed formulation is tested on two flow problems. First, the mode transitions in the circular Couette flow are investigated. Two scenarios are considered. In the first one, the outer cylinder is at rest, while the inner one spins. Two linearly unstable modes are identified. The primary mode is real and represents the axisymmetric Taylor vortices. The second mode is complex and consists of spiral vortices. For the counter‐rotating cylinders, the primary transition is via the appearance of spiral vortices. Excellent agreement with results from earlier studies is observed. The formulation is also utilized to investigate the parallel and oblique modes of vortex shedding past a cylinder for the Re = 100 flow. It is found that the flow is associated with a large number of unstable oblique shedding modes. The parallel mode of vortex shedding is a special case of this family of modes and is associated with the largest growth rate. Copyright © 2014 John Wiley & Sons, Ltd.     

Functionalized enamines—XXXII : Reaction of β-amino-α, β-unsaturated esters and amides with benzyl and cinnamyl bromides

Reactions of β-aminoacrylic esters (1–c) and amides (1d–o) with benzyl bromide 2 and cinnamyl bromide 3 give products which are dependent both upon the nature of the amine component of the enamine and, in the case of the amides, upon the amine from which the amide is derived. The β-enamino esters react with benzyl bromide to yield predominantly dialkylated products in the case of the pyrrolidine ester 1a. Reactions of the same esters with cinnamyl bromide yield mixtures of cinnamyl and 2-phenylpropenyl-substituted formylacetic esters. The enamino amides 1d–f react to yield the expected alkylated derivatives. The anilides 1i–o exhibit nucleophilic reactivity at the aniline nitrogen. A mechanism leading to the observed products is proposed.